Two types of laying equipment are available on the market for this type of application, which in particular entails introducing an optical cable into a hollow sheath.
A first type of laying device is based on the air-carrying principle (FIG. 1). Those devices pay out the cable by means of a flow of air.
Pull and blow type laying devices (FIG. 2) pay out the cable by exerting air pressure on a piston at the head end of the cable and by pushing it by means of rotating rollers.
The type of laying device shown in FIG. 1 has already been proposed for installing optical cables of different types, in particular underground, and in service ducts in buildings, but can be used only with difficulty in buildings because the space between the air injection system and the drive rollers makes the device bulky.
In each type of cable laying operation, the cable has a specific diameter and stiffness.
For example, cables laid underground have a greater diameter than cables for use in buildings.
Thus the dimensional and mechanical characteristics of the laying device referred to here are not adapted to laying cables specifically in buildings, where the working spaces are very small.
Installing optical cables in buildings may also necessitate working on the cable ducts of the building, in particular when there is a cascade of these laying devices disposed in series along the cable (FIG. 3). Cascading consists in installing a second in-line cable laying device to enhance cable laying performance when the system is at its limit.
In the device described in the patent FR 2 774 777 the air injection system is on the upstream side of the drive rollers, which are therefore placed in an airtight volume. To cascade them, those devices must be opened up to put the cable into place. When the device is closed again, sealing problems are typically encountered: a seal, a necessity in the case of that device, may not be correctly repositioned in its housing, which creates air leaks.
Moreover, that known type of device, which does not have dimensions particularly suited to its use in buildings, cannot always be installed in cable ducts. Furthermore, that type of device is not simple for the installer to manipulate. In fact, because of its overall size and its weight, that type of device is not easily maneuverable.